1. Technical Field
The present invention relates to wireless communications and, more particularly, to configuration of base stations in wireless networks.
2. Description of Related Art
More people than ever are using mobile stations, such as cell phones and personal digital assistants (PDAs), to connect to wireless networks, which are also referred to as wireless wide area networks (WWANs), cellular communication systems, radio access networks (RANs), wireless access networks, and by other names. Service providers typically operate these wireless networks to provide both voice and data services using a wireless communication format such as Code Division Multiple Access (CDMA), or another format.
In a typical wireless network, service providers operate multiple base stations, each typically including one or more towers or antennas that radiate to define a coverage area within which mobile stations may communicate with the base station over a radio frequency (RF) air interface. The base stations then act as conduits for signaling and bearer communications between the mobile stations and one or more signaling and/or transport networks, over which the mobile stations may communicate with other devices.
As a general matter, a base station may take the form of a device known as a base transceiver station (BTS), or perhaps encompass one or more BTSs controlled by a device known as a base station controller (BSC). A BTS may also be referred to as a Node-B, and a BSC may also be referred to as a Radio Network Controller (RNC); BTS and BSC are used herein as examples and for clarity of presentation. The base station may provide connectivity for the mobile station with a device known as a mobile switching center (MSC) and/or a device known as a packet data serving node (PDSN). The MSC generally acts as a switch, connecting the base station to one or more circuit-switched signaling and/or transport networks, while the PDSN would generally connect the base station to a packet-data network. Note that a base station may, instead or in addition, provide connectivity with such devices as a SoftSwitch, an IP Multimedia Subsystem (IMS), a Multimedia Domain (MMD), as well as other examples.
Furthermore, different types of base stations may be deployed in a wireless network. Typically, the most common base station is what is known as a macro base station, which would have a relatively large coverage area and provide service to a relatively large number of mobile stations. A macro base station may transmit with a power of approximately 20 watts. Macro base stations are typically arranged such that their respective coverage areas overlap, if at all, only slightly, such that, taken together, the combined coverage areas of the macro base stations blanket a particular geographic area with substantially complete wireless-network service.
Moreover, wireless networks may also incorporate smaller base stations, known as pico base stations, having a smaller coverage area than a typical macro base station and, at any given time, providing service to a smaller number of mobile stations. A pico base station may transmit with a power of only about 50 milliwatts. Pico base stations may be used for providing service to a particular building, such as a particular residence. In general, pico base stations may be placed anywhere with respect to the coverage areas of the macro base stations in the network, and thus may be characterized as “underlaying” the macro network; that is, the coverage area of a pico base station may be overlapped by the coverage area of one or more macro base stations. Note also that a given pico base station may be connected to the same network infrastructure elements—such as the same BSC for example—as one or more macro base stations, but may also or instead be connected with separate network infrastructure elements.
From time to time, a mobile station that is in communication with a given base station may cooperate with the network to perform a “handoff,” by which the mobile station switches to communicating with a neighboring base station. To inform mobile stations as to their handoff options, base stations typically broadcast a “neighbor list,” which may include pseudorandom-number (PN) offsets in use by neighboring base stations. In general, a PN offset is a numerical code that base stations use to encode—and mobile stations use to decode—information transmitted over an air interface. Typically, it is by PN offset that mobile stations distinguish among base stations, or among various sectors of a given base station.